Hi,
As we all know, difficulty is calculated from the network hashing power.
Since default mining option is to receive rewards, is it possible to forfeit the rewards to prevent an increase in difficulty?
In other words, can you "donate" your rig to BTC for "free"?
The difficulty is really calculated by how short the block time was. If it was 8 minutes, increase the difficulty. If it was twelve decrease the difficulty. For an altcoin, you could customize your client to wait after solving a block. If it waited until ten minutes had past after the last block and it was always your client that solved a block, then the difficulty would remain the same. You need to have an entity with significantly more than 50% of the hashing power to do this, or the other 50% would solve the block while yours waited, and raise the difficulty.
On altcoins this could be a good idea for a benevolent altruistic user who wants to experiment. You can actually download the whole block chain quickly on these other altcoins and do experiments. These are alternative testnets. You can get some coins to play with and if you lose those coins, who cares?