Hey Jenna, do you have some examples of activities logged by Yesware?
The way we work through this is by naming conventions in the task descriptions. If you can, for example, prefix descriptions of tasks by a product with "Yesware:" then you can set up your smart lists and triggers to only include tasks that Start With "Yesware:" as an example. If you have examples of the actual logs from Yesware, we can try some pattern recognition and suggest what you might be able to do.
In worst case, you can do something like use an Apex trigger in SFDC to change field values on the persons so you can communicate the Yesware activity to custom SFDC fields which can be visible to Marketo.
Edward Unthank | Etumos