"bi-annual subscription"?

Yes.  See here: https://www.rotax-owner.com/en/rotax-owner-community/10094-did-the-price-just-double

Grammar Police says Rotax-Owner gets a star.  Pilots are handicapped because we've been getting flight reviews and medical checks every two years, calling them "Biannual" when they're really "Biennial".  Good thing we don't have to get them biannually!

Clarity Police says "twice yearly" or "every 6 months" is the obvious correct wording.

We offer two PAID subscription options for Rotax-Owner.com to provide you with flexibility and choice:

1. Annual Subscription (1 YEAR) – $49.95 USD (billed once per year)

2. Bi-Annual Subscription (6 Months) – $29.95 USD (billed twice per year if you auto-renew, or valid for 6 months if you choose not to auto-renew)

By selecting the full-year subscription, you can save $10 compared to the Bi-Annual option.

We recognize that not everyone needs a full-year subscription, so we’ve created these 2 options.

We also offer a FREE subscription that provides email notifications for ROTAX-released Alert Service Bulletins (ASB), Service Bulletins (SB), Service Instructions (SI), Service Letters (SL), and Service Instructions for Parts and Accessories (SI-PAC), as well as other critical safety information.

All subscribers (both free and paid) receive access to the Rotax-Owner forum and blog.