My mother in law invited us in her house to stay we have been helping with the bills but the landlord had the police cite my husband for criminal trespassing is this legal

I wouldn't think so. The landlord must be failing to tell the police that the premises are being rented to your mother-in-law.

What does the mother in laws lease or rental agreement say about house guests or other people living in home. I know all of my rental agreements I use would not allow people to move in.

It is legal, the issue will be can he beat the criminal tresspass ticket, So more info is needed

I know in the apartment complexes here, if a family member is not on the lease, and not listed as such, and there are problems with them on the property, they can be issued tresspass warnings.

Certain state and federal laws prohibit limits on the number of people who can occupy a rental, depending on various factors such as number of units and whether the owner occupies one of the units, regardless of what a lease says. This gets into territory you don't want to go into, however, because the landlord can usually find reasons to evict everyone, or at the very least not renew the lease, or decide he wants the place for his own use. So.. you risk your mother losing the place by staying there.
Whether you pay bills or rent or were invited has nothing to do with all this UNLESS the landlord accepted rent directly from your husband.

The landlord can file charges. If the lease prohibits occupancy, he might make it stick. On the other hand, as long as your mother testifies she invited you to stay, it is unlikely the charges will stick or that you will even be prosecuted.