From the DCC Beta Rules, page 100
Determining spells at a new level: A wizard knows spells as indicated on table 1-12: Wizard. At each level, the wizard chooses the level of spell he wishes to learn, as limited by the Max Spell Level for his wizard level, and randomly determines which spell it is. Duplicate results may be re-rolled.
The random results reflects the cacophony of fate: a spell is a result of finding a transcription, translating and understanding it, communing with whatever powers are necessary to cast it, acquiring the requisite ingredients, and, finally, succeeding in the associated rituals. At any given time a wizard may be working on unlocking a variety of spells, but the ones in which he succeeds are limited.
In the course of his travels, a wizard may come across recordings of spells. He may steal another wizard’s grimoire. He may find etchings in a lost tomb. He may make acquaintance with a generous demon. Should a wizard have a source of knowledge for a new spell, he may choose to learn that spell when he reaches a new level instead of rolling randomly.
Learning a spell: Just because a wizard finds a description of how to cast a spell doesn’t mean he can actually pull it off. Your character must make a check to learn the new spell to which he is exposed. Your judge will give you the criteria for this check.
So, I'm reading between the lines here some. It looks like a wizard can automatically select their level-up spell if they have a copy of it floating around. But they also could learn the spell outside of the leveling processes (though the rules for learning the spell are not presented)
From DCC Beta Rules, page 140
3. The means are mysterious. Even when a wizard
learns that a spell exists, and finds a source to teach him, the process of spellcasting may be beyond his grasp. Practice, practice, practice!
4. Obtaining magical knowledge should be part of the adventure. Finding new spells and magical knowledge should be a motivational goal for any wizard player.
3 suggests that learning a news spell should be difficult and that the wizard may fail to learn the knowledge.
4 suggests that learning new spells should be a goal of a wizard.
So yeah, I think the rules are suggesting that you can learn more then your 1 spell per level limit.