Alright, first question, does GOG.com sells the gold version of JA2? There was this other thread on the forum where this dude said "JA2 Gold is JA2 and Unfinished Business, and since GOG sells both, they sell the Gold version" but according to wikipedia, JA2 Gold is:
JA2
+Unfinished Business
+The extra guns and mercs from UB are available in JA2
+More options when you select the game difficulty at the begining of the JA2 campaign
So, the question still stand: Does GOG.com sells JA2 Gold, and if not, what are they waiting for?
Second question: How long exactly is Unfinished Business? I heard some horror stories where UB is apparently a single mission long, surely, that mission is spread on several maps or something, I sincerely hope it's not just a single map.
Thanks in advance for the answers!

According to the review (from Czech website), the game has 20 missions (i.e., 20 screens to pass) with estimated time from 20 to 50 hours (if you don't go for the main target straightly).
But you can create your own maps and campaigns. You can also download some campaign created by other players.
Personally I have to give this game another chance as it seems to hard for me.

Ahhh, good to hear.

I bought it.. in manual says that is Gold pack. i saw some options of more guns and if u put a code in loggin game you play Unfinished Business.. Well, i dont really know the differance yet because i patched it with 1.13 (non official patch that transform ja2 to jag2 gold) and at least in main menu/ and game menu shows more options like one more level of difficulty.
the game is awesome! and im enjoying playing it!

Ok no problem my8. Reading the manual that came with this "Jagged Alliance2" (with a smgwoman in front cover) on gog.com version: "Jagged Alliance 2 GoldPack" on title of manual pdf: "This special edition includes both the award-winning Jagged Alliance 2 and its follow-up, Jagged Alliance 2: Unfinished Business. Differences between the two games are noted throughout the manual.." In game to play it you have a laptop style that you logon to hire and get missions.. there, you have to type a code given by manual: "The IMP access code is different in Unfinished Business than in Jagged Alliance 2. Use GP97SL insted of XEP624..."
hope that help. cya.