My interpretation is that it's OK to have your friends chip in for refreshments provided they only pay for what they get and that you don't take a share of every pot (i.e. a rake). And, of course, there is always some risk if you invite strangers to your game.

Here's the official word from the website of the Washington State Gambling Commission:

"HOME POKER GAME HOSTS AND PLAYERS

Home poker games are permitted in Washington State as long as professional gambling does not occur. The Washington State criminal code defines professional gambling as occurring when a person pays or accepts a fee to participate in a card game (RCW 9.46.0269). No fees may be charged for arranging, facilitating, organizing, or for operating the card game.

Persons who are found to be engaging in Professional Gambling are subject to criminal prosecution pursuant to the Revised Code of Washington criminal statutes. The following criminal statutes may help you determine if you are operating legally."

Note to non-Washingtonians: This is the law in Washington but may not be the same in other states which may have more or less restrictive rules.