[This is a copy of a post that also appears on the CRM Outsiders blog.]
Open Source is at the heart of SugarCRM's business. Well over half of our engineering effort produces code that is released under an OSI approved license. We have three versions of our Sugar CRM product: Community Edition, Professional Edition, and Enterprise Edition. The Community Edition is licensed under version 3 of the AGPL, and has been licensed under some version of the GPL or AGPL since early 2007. Prior to that it was available under several variants of the MPL.
SugarCRM does not release 100% of the code we develop under an Open Source license; Sugar Professional Edition and Enterprise Edition are distributed under a commercial license. This mix of Open Source and commercially licensed software offerings has allowed us to build a successful business while creating an innovative, award winning, affordable, and open CRM solution. From the beginning SugarCRM has always had this mixed model. We benefit from this model, and, as Marten Mickos says, believe that the world of Free and Open Source Software benefits as well. 
SugarCRM always makes available full source code to all of our customers. In all cases (Community, Professional, or Enterprise), our customers receive full source code to our products. In all cases our customers have the right to run our products anywhere: in their own datacenters, in our datacenters, or at any of a variety of cloud service providers. In all cases our customers own their data and have full access to their complete database. We care deeply about those rights. They are at the heart of our differentiation as a company.
Open Source code is just part of that. "Open" to us means more than source code. It's an entire philosophy about how we do business and how we empower our customers.
To riff on an analogy I originally heard from Red Hat founder Bob Young, would you buy a car with the hood locked shut and where only the dealer who sold you that car had the key? Imagine for a minute what that would mean. Only the dealer could perform regularly scheduled maintenance. You couldn't modify the engine in any way, such as tuning for higher performance or modifying it to run on alternative fuels. Imagine you were on a trip and the car broke down. While you might have the skills to fix it, or might find a local mechanic who could fix it, you wouldn't have those options. Only the dealer has the key, and only the dealer has the right to touch that engine. Imagine how frustrating that lack of control would be.
Why then would you run your business on software where you have no control? Where you are entirely at the mercy of the vendor? Where you did not control your own destiny?
At SugarCRM we are passionate about giving our customers that control. With full access to Sugar's source code, customers can take control of their own destiny. If they so choose, they can make enhancements specific to their business needs. If something breaks, they can open the hood themselves, or have a "mechanic" of their own choosing open the hood for them.
But empowering customers means not just sharing with them our source code (under either an Open Source or commercial license), but also making sure that they have the keys to the hood so they can control their own destiny. How is this different? Consider a "traditional" hosted (Software as a Service, or SaaS) CRM provider. Your data resides on their servers, under their control. If their systems go down, you go down. If it doesn't operate the way you want it to, you're out of luck. Even if they were to give you access to their source code, you are still not in control of your own destiny, because you wouldn't be allowed to modify it, or even run it, if you wanted to. You might have the blueprints, but you still can't get under the hood. Tim O'Reilly has been preaching this challenge to Free and Open Source Software for many years.  Marten Mickos makes the same observation about closed web services in his recent Computer World UK article. 
At SugarCRM our customers have not only full access to their data, but they have that access in the original database form so that they can truly control their own destiny. They can move that database to another cloud service provider or to servers on their own private cloud or in their own data center. As a SugarCRM customer that choice is in your control.
Further, our open model has created a vibrant partner network that allows our customers to select the level of service they want, while at the same time giving them full control and options for the future. For example, you may be the hands-on person who likes to open the hood and change your own oil. Or you may prefer to buy a complete service agreement with your car, where everything is included and the dealer takes care of everything. Our open model has enabled a network of partners that offer whatever level of service you need, from do-it-yourself to full service. As a SugarCRM customer that choice is in your control.
Our open, "run anywhere", model enables similar choice and control in where your data resides and your applications runs. That may mean you choose to let us run Sugar for you out of our datacenters. Or you may choose to run it on cloud services such as Amazon, Rackspace, or Windows Azure. Or you may choose to run it on your own servers on your own private cloud. As a SugarCRM customer that choice is in your control.
Bottom line: Open is a core value for us a SugarCRM. That manifests itself in part through our commitment to our Open Source Community Edition, but is pervasive in our entire company philosophy in which our customers receive full source code to our products, have the right to run our products anywhere, and own their own data. Open is at the heart of our business.
5. Open Source Needs To Have An Unfair Advantage To Succeed by Marten Mickos, https://www.computerworlduk.com/community/blogs/index.cfm?entryid=3048
6. Open Source Paradigm Shift by Tim O'Reilly, https://tim.oreilly.com/articles/paradigmshift_0504.html