Polarnavy, - Polar Navy
can read the charts
from chartworld, - assuming it's the S63 format you have bought. Polarnavy is absolutely reasonably priced at $39.99 (today's price). I tested a 3 month subscription of a small chart from chartworld, and it worked perfectly. After the subscription period ran out you can still use the chart, however it's no longer updated (no difference to outdated paper-charts or BSB-charts).
My dream is that Opencpn, - with the new plugin-architecture, might be able to read S63-charts. Maybe with a (hopefully small) pricetag on the plugin. Legal
challenges concerning copyrights I hope might be overcome with the plugin being separate from the Open source-part of Opencpn.
My other dream is that the S57/S63-format (or successors) will become the overall standard and then also priced lower than the prices at present at www.chartworld.de
. Prices for S63-charts are not yet competitive, compared to other chart-producers for my area (Scandinavia).