Mod Podge easily comes out of fabrics with water if it's still wet and with petroleum jelly if it has dried. There are other types of decoupage glues on the market, which may have different recommendations for removing unwanted glue but, typically, the same steps apply to other types of glue as well.
If craft time creates something of a mess with the Mod Podge glue, it's actually easy to clean up. If the glue is still wet, a wet wash cloth should wipe it right off. In some cases, adding a bit of dish soap will help loosen any stubborn residue. Dawn dish soap seems to work the best. If the Mod Podge is dry, start by scraping off any blobs until the hard glue comes off completely. From there, rub a little petroleum jelly into the stain, and rinse it with warm or hot water, whichever the fabric's care instructions recommend. If the jelly does not remove the stain, try Dawn dish soap. Do not dry the shirt until the stain disappears completely.
The same steps work if Mod Podge gets on furniture, tables, or other surface items. If it falls on a hard surface, sanding helps smooth out any rough edges left by the glue. Sometimes sanding isn't an option, so in that case, a good scrub with warm water and dish soap should alleviate any stains.