I know there have been several threads on this topic over the last 4 years or so, but I would like to try again.
A little background: I am the lead licensing person with Fedora (and the Fedora Engineering Manager at Red Hat). I work closely with Red Hat Legal, and interested parties like the Free Software Foundation to try to resolve licensing issues that prevent us from including otherwise high quality software into our distribution.
While the existing Open CASCADE license has a number of areas which make it completely GPL-incompatible, there is one area which makes the license non-free (and thus, not acceptable for Fedora and a number of other distributions):
Section 7 says:
You may choose to offer, *on a non-exclusive basis*, and to charge a
fee for any warranty, support, maintenance, liability obligations or
other rights consistent with the scope of this License with respect to
the Software to the recipients of the Software ....
The wording that I have highlighted in asterisks is the problem. As I said previously,
limiting this permission to "a non-exclusive basis" is bizarre. Why can't someone
choose to offer support exclusively to customer A but not any other customer? A fair
number of FOSS licenses have upstream indemnification clauses, but this goes beyond that.
The easiest fix to this license would be to drop "on a non-exclusive basis" from that sentence.
That said, the better fix would be to relicense this work under the LGPLv2+, as that would remove all of the GPL compatibility concerns and encourage wide-spread adoption of the technology.