this is tennogen. every couple of months (?) Digital Extreme will put some of these fans created skins and syandanas into the game. they'll choose the best looking, lore friendly, fit for warframe and following the rule of tennogen which as far as I know warframe body mesh (shape / model) should not be changed from the original which this skin just fail to follow. those tennogen that DE accept will appear in-game on the round end with an update and can be bought.

If the issue is you can't afford to buy on Steam, well unfortunately you must. This is tennogen and fans created this, not DE, so if we want to use their creation they need royalty from us. they don't work for DE, they simply help warfarme community alive. therefore grinding in-game won't give those creator anything.

edit: I'm not tennogen master or anything so I may be wrong