Al owns 100% of AlsCo LLC and 100k goes to his se tax
Al owns 50% of AlandBobs LLC and a loss of 10k goes to his se tax
That's a non-passive loss

AlsCo LLC has a profit sharing plan. Normally we would use 100k less 1/2 the SE tax X 20% to get the max contribution for Al

How do we treat the losses on his SE tax?

You can only consider self-employment income compensation ("earned income". i.e. from personal services) with regard to the business/partnership with respect to which the plan is established/maintained. See Treas. Reg. Section 1.401-11(d)(2)(ii).

Is that true for 415 purposes, too?

Yes--at least under the new regs. Reg. Section 1.415©-2(b)(2) says that compensation includes a self-employed individual's earned income as described in Code Section 401©(2) and its regulations. Reg. Section 1.401-11 is one of those regulations, and it limits compensation to earned income with respect to the trade or business sponsoring the plan. Deduction defintion of compensation is the same.