"Purchasing indulgences that is buying forgiveness for sins commited [sic] or that might be commited [sic] in the future also were used"
Wrong-o.
First of all, notorious persons like Dominican Johann Tetzel [1465-1519) did sell indulgences on behalf of corrupt papal fund-raising projects raising money to build St. Peter's in Rome. However, in doing so they acted contrary to explicit Church regulations. This condemnation was reiterated very severely by the Council of Trent (16th century) and the sale of indulgences was *certainly* not done in the 18th century --- the time-frame of the foundation of the Alta California missions by Fr. Serra.
Second, indulgences have nothing to do with the forgiveness of sins. Indulgences are a kind of reparation to undo the temporal harms of sins already confessed, repented and forgiven. You can't "get" an indulgence for a sin which was not already confessed, repented and absolved.
Third, the idea that indulgences constituted some kind of get-out-of-jail card for sins that might be committed in the future, is a pure absurdity, typically claimed by somebody who doesn't know jack chick about Catholicism and hasn't bothered to find out.
Brian Ball, who wrote this article, seems like he's trying to portray Junipero Serra in a favorable light, but he is embarrassingly loose about his facts.
If I were his teacher, I would send this essay back, all marked up in red, for a major do-over.
Jack Chick? No, I don't take him seriously. Some of this tracts are good for witnessing to godless but that's about it. If he had anything to do with this article it would have also mentioned real batty things.