There's also the SCP to consider.
Given that it'd take maybe 4 years to knock up a new game from scratch and that the SCP is both free and features pretty much every technological thing FS3 could have, any developer would be relying entirely on the strength of the plot for their profits.
And with the modability of the SCP releases, they'd have to expect that the entire FS3 campaign would be mirrored in an SCP campaign inside a week of it's release, complete with any new little innovations in design, control and graphics the developers happened to come up with.
Basically, the only way forward with Freespace would be with the co-operation, support and heavy involvement of the SCPeople. C'z if they kept doing their thing while someone was trying to market FS3, it simply wouldn't sell.
At present, to someone without full SCP support, I'd say the rights are worth maybe $30k tops.