RhodeCode is particularly interesting because it uses an approach proposed by Monty Widenius of MySQL AB fame: Business Source Licensing
In the RhodeCode case, the underlying functional software is all open source right now. However, several non-functional aspects of the front end (the "chrome" if you will) are not open source, but are instead under a business source license that means they will go open source automatically in a few years time. They also have a generous program to make the full version available to other open source projects and traditionally cash-strapped organisations.
This creates some really nice incentives:
traditional enterprise customers are strongly encouraged to treat it as a typical software purchase/subscription. Sure, in theory they could strip the not-yet-open-source chrome bits and replace them, but it isn't worth the hassle at the prices RhodeCode charge
other open source projects can use the full RhodeCode version free of charge
if RhodeCode ever do anything ridiculous that alienates their community, the right to fork remains available, as replacing the business source licensed chrome parts wouldn't be that difficult, and the worst case scenario is to just wait a few years until the currently business sourced parts become fully open source.