Not sure on listing forums but google is an odd thing. My site is like 80% dynamic. Google basicly has the following rules from what I can see.
Dynamic content IS ok... but BIG BIG BUT.... it can only have one querystring variable... in otherwords:
mywebsite.com/dynamic.php?key=stuff is fine.....
mywebsite.com/dynamic.php?key=stuff&category=things&type=12 is NOT ok...
in the case of ubb.... I would ASSUME.....
https://ubbdev.com/ubb/ultimatebb.php?ubb=get_topic;f=8;t=003571 is bad because the ; counts as a break and new variable...
BUT I'm not familiar with how UBB processes the query strings... maybe if you made it take all the variables and smash them together with some specific pattern that doesnt happen in ubb lines and do some sort of programatic loop to find the variables by extracting them from a single ?ubb= line then that would probably fix it...
in otherwords... if you made it send
https://www.ubbdev.com/ubb/ultimatebb.php?ubb=get_topic___f=8___t=003571 using ___ as a separator... doing some sort of regular expression based string selection looking for patterns of ___ separated stuff and then processing those..... *Shrug*
I'm guessing this would be a pretty major rewrite though..... but really only effort should be placed on the display of messages and forums.. the rest does not matter so much I wouldnt think.. possibly even some sort of google sensing code to feed out maybe a different page and when the user shows up it redirects them back into the regular stuff based on an "encrypted" string of jibberish that can be translated into normal keys? aka if ?ubb=ksmdlk2moim2#%2imomfgklm233ijorfm2klml23@#fkmo2 somehow gets translated into ?ubb=gettopic;f=8;t=15534 etc.... see "vernam encryption" coding samples found on the net as an example of what I mean if someone wants to try programming something to do something like that...just hard code the encryption key into the source since we're not really trying to secure anything.. just jam it all together... lol... but I still think that would need some sort of regular expression string manipulation...
Outside of all that stuff above... I have no other idea other then making your ubb generate static pages for the messages like the old ubb's used to do which would eat the hard drive space up big time on large forums....
And in regards to how to do the above... I dont really know... lol... Just my idea based on what I know but all bets are off on how I'd go about implementing that... lol... I dont know CGI and PHP well enough to tweak UBB to do something like that... just know that's probably how you can get around it...
you would only wanna jam that into something bots would see though...