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The usual downside is that because of the scope of any decent development environment, the particular implementation of the support module may be less feature rich than the kind of thing you could find in the third party market. Take version control, for instance. I think it would be pretty cool if I could use Git together with WinDev, so I could host a WinDev repository on GitHub, something like the DevRoadmaps Clarion Library on GitHub. But that's not an option; the only way to host a publicly-accessible WinDev repo is via SCM itself. That's fine, but SCM isn't a distributed version control system, it's a centralized version control system.
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