At the moment I can't see any other way to get the banner ads in the game but to convert the game to run in a web browser, and that is simply just not going to happen. It's about the same as starting the whole project from scratch.

Hey, on my part: I'm not even sure if this game runs on my own PC at home because the early alphas I tried out showed pretty bad performance, but I just wanted to support this game by buying it so that you have some money for further development, regardless of whether it works or not. Here I can play it pretty well, but I'm not sure how the performance with the current beta is on my own, single core PC with 1.5 gb RAM and a Radeon HD 3450 (it's pretty outdated).
Anyway, I think contacting Wolfire Games (the initiators of Humble Bundle) could be a good idea for you. I've bought all bundles since Bundle 2 so far, including the Voxatron Bundle, and I'm willing to buy every new one that comes out. In the case of Voxatron it has worked out pretty well, I think, but there's another example: Cortex Command! I had already bought it in 2009, but re-purchased it in the second Humble Indie Bundle (because I was interested in the other games in the Bundle, especially Revenge of the Titans). It's been in alpha since 2008 , I think, and development was initially started in 2000, got serious in 2004. The development went incredibly slow (about 2 builds per year). Through the Bundle they obviously got a boost and now release new builds in much shorter intervals, and their community has increased, too.

You should be able to create a socket to connect to a web server that would deliver either the address of the image on the server or the data (you could convert the image to base64 in php, as an example) and the http url to the client, and then displaying the image and setting up a hitbox on the image that will attempt to open the http url, at which point the system & browser should be able to take over.

With a little ingenuity you might even be able to find a way to make the proper referrals go through on the link click as well, but if not you could always try manually taking in ad placement requests, and they would pay a static fee based on how long they want the ad up.

Banner ads inside a game is not a good idea...

I strongly disagree.

It's a fantastic idea and I put into question the motives of anyone who dares say otherwise.

VANISHING,
You are letting personal interests get into the way of fair judgement.

Your opinion on such an important matter cannot be accepted.

BOB,
How did I let me personal interests get into the way of fair judgement? How about YOUR opinion on this matter cannot be accepted?

Reasons that I don't support ingame ads:
1. The revenue is minimal compared to other means.
2. Takes away precious space and time from player.
3. Annoys player more than simply go commercial in the long run (misclicks and all that fuss).

Putting ppv/ppc ads on the rwr site however, IS a good idea. In fact, pasik should really start doing that now in my opinion.
However, putting any kind of ads inside this kind of game IS a BAD idea. Period.

OBJECTION!

The only reason you don't want the game to be free is because you already paid for it!

Revenue is a costant stream dependant on community size, which has good chances to be pretty bloody big if the game goes free, plus if ads are done right they will take NO time since they would just be taking up unused space.

A free game with ads is going to make what? 1% of the fanbase leave.
The demand of money instead will hunt away a crushing majority of possible players.

Quit contaminating the issues with your biased foolishness, this cour should have none of it.

Making the game free based on in-game ads needs a lot of work, frankly I don't think that's something I'll start to implement. Getting clicks on the ads is pretty far fetched in the first place.

There needs to be another way to play the game free, likely based on limiting content and functionality.

In the long run that will make people leave too.

Look at World of Tanks: free players in that game are (literally) cannon fodder for those who pay and receive what are nothing other than hacks.

"Legalizing" hacking is not the way.

I am wondering where did you get those stats? 1% of the fanbase? Please don't randomly pull numbers out of your ass.
The demand of money is what that got amnesia, penumbra, terraria, minecraft the position they are in now, not free to play.

You are talking like commercial is evil, if this is the way, then your logic is clearly messed up.

In fact, I wonder if you HAVE paid yet, if not, you are in no position to question my motives where you just want to play a free game.