Can I response the job if I don't have account on website / if I don't want to post my resume?

Yes. You can send a resume to any job without signing up. It is enough to have a resume file in your computer or in the cloud storage. To respond to a job go to its description and click Send Resume button. Next, specify the path to where you want to upload resume file: it could be your PC or cloud Google Drive and Dropbox.

You can also respond to a job with LinkedIn. To do this, you need to go to the job page, click Send Resume and select LinkedIn in the pop-up window. You will open the authorization page, here you need to enter the login information. After that, the basic information from your profile on LinkedIn (and photos including) will be pulled up into the response form, you can edit it and send it to the employer.