Legal Question in Technology Law in California

Assuming this is (or was) a general partnership, which is likely if it were an unincorporated business (and not an LLC) run by two or more people with an (original) intent to share profits and losses, then your recourse is outlined in the California Revised Uniform Partnership Act, sometimes called the RUPA. It is part of the Corporations Code. See sections 16100 through about 16807.

Generally speaking, you'll have to enforce your rights by filing and serving a lawsuit, citing violations of the RUPA and/or your partnership agreement. The lawyer you retain to write up and file the lawsuit may advise writing a demand letter before suit. Negotiation or mediation might be an alternative to suit. Also, possibly your partnership agreement contains an arbitration clause.

A lawsuit against a business partner will usually allege causes of action for one or more of the following: breach of contract; breach of fiduciary duty; actual fraud; constructive fraud; failure to comply with specific duties and procedures specified in the RUPA such as giving you access to the books and records, or using partnership property as though it were his own; a request for dissolution of the partnership; and for an accounting.

Most suits between (former) partners are settled out of court, before trial, with the assistance of the parties' lawyers, the judge assigned to the case, and court-appointed mediators.