In the most extreme cases, i.e. FreeBSD->MacOSX, the free software is replaced by software under a non-free license. If there is mention of how libcrurl will be licensed, I missed it, but there's actually a subtler attack on free software which has happened with i.e. GCC->Clang or Konqueror->Safari/Chrome. What makes this attack subtle is that it allows companies to release under a free license, while not actually making any commitment to a free ecosystem. By providing massive amounts of funding and manpower to these projects, large companies can ensure that their version of the software remains dominant, and they get to choose what to include and exclude. This has predictable results: breaks in support for related free software[1] and pressuring the introduction of non-free components even in otherwise free browsers[2] after people have committed to the new, corporately-controlled platform.
As noted, I don't know what license this will be released under, or how this power will be used if they supersede the original curl tool. I'm just saying that projects like this should be seen as attacks on free software and viewed with suspicion.
[1] https://bugs.kde.org/show_bug.cgi?id=365327
[2] https://blog.mozilla.org/blog/2013/10/30/video-interoperabil... (note: OpenH264 is free as in beer not free as in freedom, a.k.a. gratis not libre).