You can easily change the text that appears on your Subscription widget on the product page.
For international stores that are not using English, you can use this to replace the text with your language.
Legacy Themes (not 2.0):
Step 1: From Ongoing, click Settings and then Subscription Widget
Step 2: Type in your new custom text under the Subscribe and Save Badge. You can replace the text to say whatever you would like it to display
Step 3: Click Save
2.0 Themes (such as Dawn):
From Shopify Admin, under Online Sales click on Themes
Click Customize on your Live Theme.
From the drop down menu click on Product, then Default Product.
In the Product Information section, click on the Ongoing app block called Subscription Plans
In the Subscription Purchase Label you can type in your new custom text in the text fields, and click Save.