Selling your software is completely your decision, if you sell your business and 99% of it is dependent on your software, selling the business without it will be loss for you. Besides if it is less than 50% of the business you can negotiate it with your buyer.
You can use these links if you are serious about selling your publishing business: https://www.businessbroker.net/keyword/magazine-and-publishing-businesses-for-sale.aspx
https://www.businessesforsale.com/search/publishing-businesses-for-sale
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath