What about this:

Current IB licensing uses license keys installed into the server to control
maximum simultaneous connections. Assuming that application vendors depend
on this scheme now for their application licensing, if it continued they
would be satisfied, right?

OK, if that is true, then the challenge becomes one of allowing any vendor
to take over the previous role of IB Corp - that of generating and issuing
license keys. We can do that by enhancing the key generation process to
include a vendor supplied key value. Each application vendor could supply
this vital part of the key generation/validation process. Servers installed
by this vendor would then only work using license keys generated by them.
Applications made by these vendors would only work with servers that were
using their licensing keys. The valid keys need only be recognized in some
way by the applications and the server code. This seems to be relatively
small adjustment to the current scheme since the licensing tool already has
key checking code in it.

Those application vendors who do not need to be bothered by this can opt
for an alternative option in building their servers without the licensing
module included. Those versions of the server code would not work with the
above client applications, however, unless the customer went to the effort
of spoofing the valid license key values. In the end, any customer who
actually does this is not going to be stopped for long by any better scheme.