Game File: 

Jumper OF.7z

(NOTE: contains some gory graphics in World 5 and maybe the intro cutscene, much nicer outside of that)

The classic Jumper fangame you love and love now has a download link on a site that still exists! Not only that, but this site has NO sketchy malware whatsoever! And if that's not enough bang for your lack of buck, said download link is also completely free of viruses! (virodes?) It DOES force your screen resolution to 600x480 or somewhere around that, but it kindly reverts back to your main resolution once you stop playing it. The download link, Jumper OF.7z, is just above this text!

But what IS Jumper: Opposing Forces? According to the readme,
"Jumper Opposing Forces is created as a spin off from YoMamasMama's popular Jumper Games. Its taking time during the J1 timeline and puts you in charge of two different characters. The gameplay is very similar to what you are familiar with, if you have played any of the other games, so hopefully you will feel at home with it. Be warned though, the game is rather hardcore so it will be quite a challenge to run through it."
What that fails to mention is that it's also a crossover with Half-Life, and there's one area in particular with a lot of fictional-creature-gore in it. If that all sounds okay, then go ahead!

But wait, is all this still not enough? Really? Like, rea- an additional savefile with ALL the Get Ogmo stages beaten, SEVERAL Thief Mode stages also beaten, and ONE secret character unlocked is also available, so now you can have even more resources for the built-in level editor! Download it HERE BUT PLEASE DO NOT CONFFUSE THIS WITH THE DOWNLOAD FOR THE FULL GAME, WHICH YOU CAN FIND ABOVE THIS TEXT! Anyways, if you get more progress on that savefile, feel free to re-upload it in the comments! Yeah!

But wait AGAIN, I don't know if it runs properly on Mac/Linux, nor do I know if any Mac/Linux downloads exist. Sorry.

Upon downloading, extract the .7z file using 7-zip. Or go find and use PeaZip and in case this message is being viewed in an apocalyptic future where 7-zip has no official download site either.