My understanding is that what you describe is completely legal.
ZFS on Linux is a good example of this. ZFS and the Linux kernel are both open source, but their licenses are incompatible with one another—ie, you can't combine the code.
A common workaround for this problem is to compile the source on the user's machine. When you install ZFS in Debian, apt will automatically download the ZFS and Linux source code, recompile the kernel with ZFS included, and install the result. This is all completely invisible to the user, except for the absurdly long install time.
ZFS on Linux is a good example of this. ZFS and the Linux kernel are both open source, but their licenses are incompatible with one another—ie, you can't combine the code.
A common workaround for this problem is to compile the source on the user's machine. When you install ZFS in Debian, apt will automatically download the ZFS and Linux source code, recompile the kernel with ZFS included, and install the result. This is all completely invisible to the user, except for the absurdly long install time.